Chukrasia tabularis is an economically important tree and widely cultured in the southeast of China. Its barks, leaves, and fruits are consumed as a traditional medicine and perceived as a valuable source for bioactive limonin compounds. The extracts from root barks of C. tabularis showed significant anti-inflammatory effect. The aim of this research was to explore the material basis of C. tabularis anti-inflammatory activity, and to purify and identify anti-inflammatory active ingredients. By a bioassay-guided isolation of dichloromethane fraction obtained two novel phragmalin limonins, Chukrasitin D and E (1 and 2), together with 12 known limonins (3-14). The chemical structure of these compounds is determined on the basis of extensive spectral analysis and chemical reactivity. In addition, the activities of these isolated limonins on the production of nitric oxide (NO), tumor necrosis factor alpha (TNF-α), and nuclear factor kappa B (NF-κB) in RAW264.7 cells induced by lipopolysaccharide (LPS) were evaluated. Limonins 1 and 2 indicated significant anti-inflammatory activity with IC50 values of 6.24 and 6.13 μM. Compound 1 notably inhibited the production of NF-κB, TNF-α and interleukin 6 (IL-6) in macrophages. The present results suggest that the root barks of C. tabularis exhibited anti-inflammatory effect and the limonins may be responsible for this activity.

Quzhou Aurantii Fructus (QAF) has a long history as a folk medicine and food for the treatment of liver diseases. While our earlier study provided evidence of hepatoprotective properties contained within the flavonoids and limonins constituents in QAF, the potential preventative effects afforded by essential oil components present within QAF remains enigmatic. In this study, we prepared Quzhou Aurantii Fructus essential oil (QAFEO) and confirmed its anti-inflammatory effects on liver inflammation through experimentation on lipopolysaccharide and D-galactosamine (LPS/D-GalN) induced acute liver failure (ALF) mouse models. Using RNA-sequence (RNA-seq) analysis, we found that QAFEO prevented ALF by systematically blunting the pathways involved in response to LPS and toll-like receptor signaling pathways. QAFEO effectively suppressed the phosphorylation of tank-binding kinase 1 (TBK1), TGF-beta activated kinase 1 (TAK1), interferon regulatory factor 3 (IRF3), and the activation of mitogen activated kinase-like protein (MAPK) and nuclear factor-kappa B (NF-κB) pathways in vivo and in vitro. Importantly, QAFEO substantially reduced myeloid differentiation primary response gene 88 (MyD88)- toll-like receptor 4 (TLR4) interaction levels. Moreover, 8 compounds from QAFEO could directly bind to REAL, TAK1, MyD88, TBK1, and IRF3. Taken together, the results of our study support the notion that QAFEO exerts a hepatoprotective effect through inhibiting LPS-mediated inflammatory response.